Drum washers are pieces of equipment which operate to effect high efficiency washing of paper pulp, or like slurries. Typical drum washers--such as those sold by Kamyr, Inc. of Glens Falls, N.Y. under the trade designation "M-57 Washer" include a rotating drum having an outer perforated peripheral surface on which the slurry is collected and through which wash water flows, and an inner portion generally concentric with the drum outer perforated peripheral portion at least at the ends thereof. A stationary suction box is provided mounted within the hollow interior of the drum at least at each end thereof, and is connected to a source of vacuum which operates to apply a suction on the drum peripheral portion to cause the slurry solids to cling to the drum peripheral portion as the drum rotates out of a vat. First and second stationary annular sealing surfaces are associated with each suction box, spaced from each other in a dimension parallel to the horizontal axis of the drum, and the rotating drum includes sealing surface means and means for connecting the sealing surface means to the drum for rotation therewith.
The sealing surface means typically used in the prior art are stainless steel blocks, and are welded to the drum, primarily to the drum inner portion and a flange extending radially inwardly from the outer peripheral surface and spaced outwardly from the axialmost outward edge of the drum inner portion. While such drum washers have been commercially successful, there is a higher incidence of failure than desired. According to the invention, it has been recognized that corrosion of the sealing surfaces is the most significant cause of long term breakdown in conventional drum washers, like the Kamyr M-57 washer. Despite the fact that stainless steel is used in such sealing mechanisms, they still corrode in the drum washer environment, being subjected to the pulp slurry, washing liquids, and other chemicals, and when they are subjected to corrosion the seal is ruined thereby eventually making the drum inoperable since sufficient vacuum cannot be applied to the outer peripheral surface.
According to the present invention, the problem associated with conventional drum washers, such as the Kamyr M-57 washer, are solved in a relatively simple yet effective manner by providing high metallurgy sealing surfaces, and a system of mechanical fastening components capable of properly fastening the high metallurgy sealing surfaces in place without the necessity of welding. Typically the sealing surfaces are made of sealing blocks of titanium or polytetrafluoroethylene ("TEFLON"). In any event, the high metallurgy sealing surfaces have corrosion resistance properties that are significantly greater than those of stainless steel.
The corrosion resistant (e.g. titanium or polytetrafluoroethylene) sealing means according to the present invention are connected to the drum by aligned through-extending openings--with mechanical fasteners through them--at one portion of the sealing body, and a lip can be provided on the sealing body for engaging the outer edge of the drum inner portion. At the opposite side, connection is provided by a radially outwardly extending flange which engages the radially inwardly extending flange from the drum outer peripheral portion, in face to face relationship, and there are aligned through extending openings in the flanges which receive mechanical fasteners.
Alternatively, the sealing means body according to the invention may have a smooth outer convex face which engages like face portions associated with the drum interior portion, with through-extending openings and mechanical fasteners through them at the axially innermost edge of the body, and with tapped openings disposed adjacent the axially outermost edge of the body. Screw threaded fasteners extend through an axial surface of the drum inner portion to engage the tapped openings.
The invention also contemplates a sealing mechanism per se comprising an apertured annular integral body curved about an axis, and of a material having corrosion resistant properties significantly greater than those of stainless steel (e.g. consisting essentially of titanium or polytetrafluoroethylene), and comprising a concave inner face, a convex outer face, and means defining openings therein for receipt of mechanical fasteners for fastening the body to another structure. The invention also contemplates a stainless steel drum, per se, having a sealing mechanism as described above.
It is the primary object of the present invention to provide an improved sealing mechanism, particular for sealing surfaces between the rotating drum and stationary suction box of a drum washer. This and other objects of the invention will become clear from an inspection of the detailed description of the invention, and from the appended claims.